<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title>束庆乐</title>
        <style>
            p{
                color: blue;
                text-align: center;
            }
            .marked{
                background-color: red;
            }
            .marked p{
                color: white;
            }
            p.marked{
                text-decoration: underline;
                height: 50px;
                line-height: 50px;
                max-height: 100px;
                width: 600px;
            }
        </style>
    </head>
    <body>
        <p>蓝色居中</p>
        <div class="marked">
            <p>非蓝色</p>
        </div>
        <p>所有 class="marked"元素内的 p 元素指定一个样式，但有不同的文本颜色。</p>
        <p class="marked">带下划线</p>
    </body>
</html>